package com.commons.utils;


import javax.crypto.Cipher;
import javax.crypto.SecretKey;
import javax.crypto.SecretKeyFactory;
import javax.crypto.spec.DESKeySpec;
import javax.crypto.spec.IvParameterSpec;
import java.nio.charset.StandardCharsets;

/**
 * 加密
 */
public class EncryptUtils {

    private static final String STR_PARAM="PassW0rd";

    private static Cipher cipher;

    private static final IvParameterSpec IV = new IvParameterSpec(STR_PARAM.getBytes(StandardCharsets.UTF_8));


    private static DESKeySpec getDesKeySpec(String source) throws Exception{
        if(source==null||source.length()==0){
            return null;
        }
        cipher =Cipher.getInstance("DES/CBC/PKCS5Padding");
        String str=STR_PARAM;
        return new DESKeySpec(str.getBytes(StandardCharsets.UTF_8));
    }

    /**
     * 对称加密
     */
    public static String desEncrypt(String source) throws Exception {
        DESKeySpec desKeySpec=getDesKeySpec(source);

        SecretKeyFactory keyFactory=SecretKeyFactory.getInstance("DES");

        SecretKey secretKey=keyFactory.generateSecret(desKeySpec);

        cipher.init(Cipher.ENCRYPT_MODE,secretKey,IV);

        return byte2hex(cipher.doFinal(source.getBytes(StandardCharsets.UTF_8))).toUpperCase();
    }

    /**
     * 对称解密
     * @return
     */
    public static String desDecrypt(String source) throws Exception{
        byte[] src=hex2byte(source.getBytes(StandardCharsets.UTF_8));
        DESKeySpec desKeySpec=getDesKeySpec(source);
        SecretKeyFactory keyFactory=SecretKeyFactory.getInstance("DES");
        SecretKey secretKey=keyFactory.generateSecret(desKeySpec);
        cipher.init(Cipher.DECRYPT_MODE,secretKey,IV);
        byte[] retByte=cipher.doFinal(src);
        return new String(retByte);
    }

    private static String byte2hex(byte[] inStr){
        String stmp;
        StringBuilder out=new StringBuilder(inStr.length*2);

        for(byte b:inStr){
            stmp=Integer.toHexString(b&0xFF);
            if(stmp.length()==1){
                //如果是0至F的单位字符串，则添加0
                out.append(0).append(stmp);
            }else {
                out.append(stmp);
            }

        }
        return out.toString();
    }

    private static byte[] hex2byte(byte[] b){
        int size=2;
        if(b.length%size!=0){
            throw new IllegalArgumentException("长度不是偶数");
        }
        byte[] b2=new byte[b.length/2];
        for(int n=0;n<b.length;n+=size){
            String item=new String (b,n,2);
            b2[n/2]=(byte)Integer.parseInt(item,16);
        }
        return b2;
    }
}
